Recent mobile devices, as typified by smart phones, are increasingly multifunctional and store a variety of information therein. Accordingly, a security function for protecting stored information from unauthorized operations or the like by a third party is essential for such mobile devices.
Generally, the security function is implemented by execution of personal authentication (hereinafter also referred to simply as “authentication”) using a password when, for example, the device is activated or returns from its suspended mode. However, the password input operation is troublesome, and imposes a significant burden on the user.
The security function may also be implemented by biometric authentication that uses biometric information such as fingerprints. In this case, if a copy of the biometric information is made, authentication will be successful by using the copy, which in turn results in reduced security. Also, the apparatus for performing biometric authentication results in cost burden.
In view of the above, a method has been proposed in which a mobile device automatically performs personal authentication by utilizing the fact that the motion of a mobile device detected while the user is walking varies from user to user (see, for example, Patent Literature (PTL) 1). PTL 1 discloses a method for controlling an authenticated state of a mobile device by comparing acceleration information detected by an acceleration sensor included in the mobile device with a walking pattern indicating acceleration information of when the user who should be successfully authenticated (hereinafter referred to as the “authenticated user”) is walking.